Chlorine dioxide is known to be a disinfectant as well as a strong oxidizing agent. The bactericidal, algecidal, fungicidal, bleaching and deodorizing properties of chlorine dioxide also are well known.
Gaseous chlorine dioxide in low concentrations such as up to about 1000 ppm has been recognized as useful for the treatment of odors and microbes. Thus, chlorine dioxide is commonly used as a disinfectant or fumigant in a number of applications and environments. Chlorine dioxide is particularly useful for the control of microbes and/or organic deodorants on and around food products during and after the packaging process. It has been reported that chlorine dioxide functions without the formation of undesirable side products such as chloramines or chlorinated organic compounds that can be produced when elemental chlorine is utilized. For example, a low concentration of chlorine dioxide gas can be maintained in contact with fresh produce for several days during shipping from the farm to the local retailer thereby reducing the rate of spoilage of the produce. In addition, chlorine dioxide gas is considered to be safe for human contact at the low concentrations that are effective for deodorization and for most antimicrobial applications.
The chlorine dioxide gas can be toxic to humans at concentrations greater than about 1000 ppm, and it can be explosive at concentrations above 0.1 atmosphere. Therefore, chlorine dioxide gas is not manufactured and shipped under pressure like other industrial gases, and conventional methods of on-site manufacture require not only expensive equipment, but also high levels of operator skill to avoid generating dangerously high concentrations.
It has been suggested that the chlorine dioxide which is useful for the treatment of odors and microbes can be generated from metal chlorites such as sodium chlorite, and compositions have been suggested which comprise mixtures of metal chlorides and other solid materials where the chlorine dioxide gas may be generated under control conditions at low concentrations. For example, it has been suggested that such mixtures of chlorites and solid materials can be maintained for an extended period of time without generation of chloride dioxide until exposed to an activating agent such as water, and when exposed to water, the compositions provide a controlled and sustained release of chlorine dioxide gas. Accordingly, such compositions can be prepared in advance and stored under dry conditions without the premature release of chlorine dioxide gas. In this manner, the requirement for skilled personnel to prepare the chlorine dioxide on site is avoided, and shelf life is enhanced.
U.S. Pat. No. 6,077,495 describes a method, composition and system for generating chlorine dioxide gas in a control release manner by combining at least one metal chlorite and a dry solid hydrophilic material which reacts with the metal chlorite in the presence of water vapor, but does not react with the metal chlorite in the substantial absence of liquid water or water vapor, to produce chlorine dioxide gas in a sustained amount of from about 0.01 to 1000 ppm.
U.S. Pat. No. 5,631,300 describes a process for preparing a composite for preventing growth of bacteria, molds, fungi and viruses by dissolving a chlorite salt in an organic hydrophilic material, and then mixing the hydrophilic material with a hydrophobic material containing an acid releasing agent. U.S. Pat. No. 5,914,120 describes composite for controlling microbiological contamination which comprises a hydrophilic material containing an alpha-amino ether, alpha-amino alcohol or alpha-amino ester and a chlorite salt, and a hydrophobic material containing an acid releasing agent. The hydrophilic material is described as being capable generating and releasing chlorine dioxide gas after hydrolysis of the acid releasing agent. U.S. Pat. No. 5,980,826 describes a method for retarding bacterial, fungal and viral contamination and growth in molds on the surface of a material and/or deodorizing the material by treating a surface with a composite which does not release chlorine dioxide in the absence of moisture, and thereafter exposing the treated surface to moisture to release chlorine dioxide from the composite into the atmosphere surrounding the material. The composites which are described in the '826 patent comprise a hydrophilic material containing chlorite anions and a hydrophobic material containing an acid releasing agent.
U.S. published application 2000/0021819 A1 describes compositions and methods for disinfecting and deodorizing a treatment area with a chlorine dioxide producing composition which comprises a mixture of amorphous calcium silicate, a chlorite salt and an activator wherein the activator includes an acid. The chlorine dioxide producing compositions may be packaged as a tablet, permeable sachet, or a permeable patch attached to a plastic bag. The compositions generate chlorine dioxide when exposed to moisture.